Question

a task in 15 days and Vinod takes 20 days to complete the same task. If they both work on this task together for 5 days then the fraction of the task which is incomplete is?

Answer 1

Answer: $\frac{5}{12}$

Step-by-step explanation:

A’s 1 day’s work = $\frac{1}{15}$

Vinod’s 1 day’s work = $\frac{1}{20}$

So, (A + Vinod)’s 1 day’s work = $\frac{1}{15}$  + $\frac{1}{20}$  = $\frac{4 + 3}{60}$  = $\frac{7}{60}$

We are given that, they both work on the task together for 5 days .

∴ (A + Vinod)’s 5 day’s work = $\frac{7}{60}$  * 5 = $\frac{7}{12}$  

Thus,  

The fraction of the task remaining task is,

= 1 – $\frac{7}{12}$  

= $\frac{12 - 7}{12}$  

= $\frac{5}{12}$